Papers, photographs and the effects of Captain Julius Morris Green of the Army Dental Corps, relating to his espionage activities on behalf of the British Directorate of Military Intelligence Section 9 (MI9) while a prisoner-of-war at Colditz and other camps in Germany, will be sold at Bonhams on June 18 in Knightsbridge for £4,000 to £6,000.The archive consists of 40 autograph coded letters by Green to his parents, John and Clara Green of Dumferline, and a few to his sister Kathleen. The correspondence runs from May 1941 through to 1944, while Green was a prisoner-of-war, at many camps including Oflag IV-C (Colditz Castle), where he was imprisoned in 1944-45, Bau und Arbeits Battalion 21 (Blechhammer), Stalag VIII-B (Lamsdorf), Stalag X-B (Sandbostel), Marlag und Milag Nord (Westertimke ), and Kgf.B.A.B.20 (Heyderbreck).

Being a dentist, he was in an especially good position to carry out such espionage work; as he spent much of his time travelling from camp to camp, treating patients. After the war, he was to present a portion of his papers to the Imperial War Museum.

The letters sometimes read like a caricature of a faulty language manual, and had the German censors employed someone with a native command of English they would have immediately spotted that something untoward was going on, a fact of which (as he tells us in his memoir) Green himself was all too aware. The risks he was running, as a Jewish prisoner-of-war in Nazi hands, hardly bear thinking about. Under the surreal humour of his letters lies horror and quite extraordinary bravery.

Julius Morris Green was born in 1912 and spent his early childhood in Killarney where his father had a dental practice. He studied at the Dental School of the Royal College of Surgeons in Edinburgh and was practising in Glasgow when he joined the Territorial Army in 1939, being posted to the 152 (H) Field Ambulance of the 51 Highland Division. He was captured with his brigade at St Valery in June 1941 and spent the remainder of the war in a succession of camps, his misbehaviour meaning that he eventually received the honour of being confined to Oflag IV-C, better known as Colditz.

His far more serious lack of co-operation, for which he would have faced certain death, can be traced back to January 1941, when at Ilag VII (Tittmoning) he was taught the code used to communicate with MI9, the War Office department tasked with aiding resistance fighters in enemy occupied territory and gathering intelligence from British prisoners of war.

In communicating with Green, MI9 usually used the conduit of his parents in Scotland. Round about the time he is trouble with the German authorities and is sent to Colditz, their anxiety is clearly making itself felt, and the operatives of MI9 hasten to reassure them: "Thank you very much for your letter of the 28th March. We quite understand your very natural anxiety regarding your son's intentions, however Capt. Green appears to be a young man of great resource and we think can he relied upon to handle the situation competently... Please try not to worry. We will do everything we can to help from this end and we have great confidence in your son" (31 March 1944).